With the development of industry, science and technology, various electronic products and electronic equipment such as household appliances appear constantly. However, the various electronic products and household appliances require different operating voltages, some needs the direct current, while some needs the alternating current for normal operation. Moreover, the values of the operating voltages required by different electronic equipment are also different. Therefore, an alternating current step-down circuit has been developed to process the alternating current, so as to generate alternating or direct currents of different voltage values to meet the requirements of different electronic equipment, so that the alternating current step-down circuit has received considerable attention and popularity. However, the existing alternating current step-down circuits are generally large and complex, are high in design and manufacture cost, have a single function and can only provide an alternating or direct current voltage, thus leading to a poor user experience.